Hinges are known with two pivotably connected hinge members for pivotably connecting two objects, such as a door and a door frame, and with thrust bearings that prevent relative movement between the hinge members along their axes of rotation. U.S. Pat. No. 3,402,422, for example, teaches a continuous hinge with two hinge members mounted rotatably about edges of a C-shaped, elongated clamp that defines an internal channel. Gear segments at edges of the hinge members are meshed with each other. One or more thrust bearings disposed in recesses of both hinge members prevent relative longitudinal movement of the hinge members along their axes of rotation. The bearings occupy most of the cross-sectional space within the clamp and have bearing surfaces on their ends that are generally parallel to, abut, and support the recess end surfaces of the hinge member recesses. The general profile of these bearings is shaped to receive the clamp edges about which the hinge members are mounted. Another configuration of a continuous hinge is taught in U.S. Pat. No. 4,999,879, which discloses hinge members with gear segments meshed with the clamp instead of, or in addition to, being meshed with each other.
During normal use, one hinge member usually supports the other via the bearings as, for example, when a door hangs from one hinge member and a wall supports the other. In this condition, the hinge members are biased in opposite longitudinal directions along the clamp length. As a result, the hinge members apply opposite forces to each side of the bearings. The bearings thus tend to twist within the clamp member, forcing the bearing surfaces out of parallel with respect to the recess surfaces. Due to the decreased area of twisted bearings supporting the hinge members, hinge wear is accelerated and unwanted longitudinal displacement occurs between the hinge members causing the door to sag. This affects the alignment of the lockset and other door hardware which may be attached, such as automatic door closers and the like. Further, gaps form between the bearing and the hinge members that decrease sealing against liquids or gasses between the bearings and the hinge members.
Ordinarily, a close fit between the cross-sections of the thrust bearings and the clamp resist this bearing twisting. Certain design considerations, however, restrict the provision of this desired close fit. For example, an allowance between the dimensions of the bearings and the clamp must be provided to permit hinge assembly by sliding the clamp over the geared ends of the hinge members with the bearings already in place within the recesses. Also, variations in the forming processes employed to manufacture different parts of the hinge hinder the attainment of uniform parts and precision fits, particularly in long continuous hinges. The spacing between the clamp ends about which the hinge members pivot is also subject to variation as the clamp must accommodate irregularities in the cross-section of the hinge members. The hinge member cross-sections also deviate due to anodizing or paint coatings of various thicknesses. Clamp members must thus be manufactured to accommodate a wide range of hinge-member gear cross-sections. In addition, the clamp itself may become bowed upon manufacturing or installation, and in some applications, loose-fitting clamp members may be desirable to facilitate friction-free hinge motion or the easy assembly of particularly long lengths.
Further exacerbating the decreased resistance of the bearings to twist within hinges built for high load applications, numerous, longitudinally short bearings are employed in order to spread the elevated loads over as many bearing surfaces as possible, which can decrease the pressure and friction on each bearing. Such short thrust bearings are even more prone to undesirable rotational displacement within the clamp member than longer bearings because the bearings must travel through a greater angular arc to cover the same distance before the sides of the bearings contact the clamp, stopping further rotation. In some arrangements, the requisite clearance between the ends of the clamp member and the bearing profile described above, coupled with bearings which are not long enough to contact a clamp wall even after moderate rotation, the bearing rotation stops when the bearings are compressed between two opposing corners of a pair of recesses.
U.S. Pat. No. 4,999,878 teaches an integral thrust bearing assembly in which multiple thrust bearing bodies are rigidly connected by webs. This arrangement increases the overall length of the assembly, better resisting twisting of the individual bearings within the clamp member, but the arrangement does not take advantage of the additional space within the clamp between each such assembly, and has certain limitations imposed by the requirement that recesses in the hinge members must be machined in the same multiples required by each such bearing unless other steps are taken to provide single or multiple bearings of other multiples.
Continuous hinges are also known in which a short lip protrudes from each longitudinal end of the bearings within the clamp. An example of this is shown in FIG. 4 of the '878 patent, although these lips are most often used with single bearing bodies. A similar lip can also be seen in FIGS. 10 and 11 of U.S. Pat. No. 4,976,008. The lips protrude just far enough so that they do not fit through the recesses in which the bearing body is to be placed. These lips facilitate assembly of the hinge because they permit a hinge builder to join two hinge members and position the bearing into the aligned recesses until the lip contacts a portion of the radius of the gear tips of the hinge members, automatically aligning the bearing for receiving the clamp edges as the clamp is slid thereover. At that point, insertion of a bearing into a recess is stopped, and the clamp can be slid over the hinges without having to align each bearing individually. Because the length of the lips are merely large enough to aid in the hinge assembly, they are not long enough to control or significantly affect rotation of the bearings within the clamp as the hinge members are loaded. The lips are usually shorter than 1/32 inches and less than 1/25 the length of the bearing body to avoid undue friction or interference with the motion of the gear sectors as the hinge is operated.
Thus, there remains a need for hinges that can prevent twisting of thrust bearings, and wear produced thereby, due to hinge members that are biased in opposite directions along the clamp length. The present invention provides solutions to this problem.